I just read an entry on "cross platform" from Wikipedia, in which it wrote:

Just because a particular operating system may run on different computer architectures, that does not mean that the software written for that operating system will automatically work on all architectures that the operating system supports.

I have seen sentence construction "Just because...does not mean" quite often, but it was my first time to notice that the word "that" or "it" could be present in the construction as well (e.g., "Just because..., that/it does not mean").

6 Answers
6

My analysis of it is that neither "that" nor "it" belongs in the sentence, and neither does the comma.

Usually when you use the "just because X does not mean Y" construct, the "X" part is so long that there's the desire to stick in a "that" or an "it" to reiterate that you're referring back to an actual noun. Otherwise it feels like the back half of the sentence floats without a noun. Note also that the comma doesn't belong there either: That's a verbal tic, a pause for breath, not a grammatical construct.

(EDIT: Just to be clear on this, I think both the "that/it" and the comma are the result of writing as though the writer were speaking. In speech it might feel necessary to breathe and then restart the half-completed sentence with "that" so that you have a subject noun.)

However, just because the forward part of the "just because...does not mean" sentence is so ridiculously long and convoluted that nobody in their right mind could ever possibly follow it and still have the original piece of the structure in their heads does not mean that people can't actually follow it if they're accustomed to the "does not mean" tag on the end.

As a caveat, I'm not really sure how the grammar fits together for this kind of construct. If I were trying to produce something in idealized English grammar, I think I'd say "X may be true, but that does not mean that Y is also true". In a case like that, the "that" is clearly needed as the subject noun of "does not mean".

The problem, as I see it, lies with the use of because. Let’s take a simpler sentence:

Just because you’ve passed an exam, (that) doesn’t mean you know everything about the subject.

If we leave out the that, there’s still a problem which first has to be resolved. We’re asking the clause Just . . . exam to be the subject of doesn’t mean. That's awkward, and I'm not sure I can analyze it adequately, but it's perhaps best understood by reading the clause as if it were in quotation marks. The insertion of it or that is a relatively trivial matter, being just a different way of packaging the information in the way jprete has so well described. The OED has at least two citations showing the construction:

Just because they put a new, refined blah-blah diesel engine in, it
doesn't mean it is going to set the world alight.

and

Just because a drug is sold at the chemist, that doesn't mean it's
risk-free.

All such usages of just because are idiomatic, and open to criticism on grammatical grounds. The word just, could be replaced by merely, or simply in OP's construction, or omitted completely. This would have no effect on the grammaticality or otherwise of any such phrasing, but...

Because X, doesn't mean Y. (by now more people would like to see "that" before "doesn't").

And the fact of the negation itself is also grammatically irrelevant. Remove it and we're left with...

In short, it's never going to be grammatical, because any clause based on the word "because" is a relational clause - as is any clause introduced by "means", or "doesn't mean". So what we have is two relational clauses, where each really needs to be related to an existential clause (something independently defined, that the relational clause relates to in its specified way).

The answers written by Barrie England and Peter Harvey are better than the anecdotal one currently accepted, but some more details on the grammar may be of use, so I'm reposting my answer (well, it's slightly modified) to one of the other identical questions.

The word "because" is a subordinating conjunction — words of this type are used to create dependent clauses (also called subordinate clauses), and that's what the phrase "Just because A" is. Clauses like this attach to the main part of the sentence — the independent clause. Wikipedia on dependent clauses:

In linguistics, a dependent clause (sometimes called a subordinate clause) is a clause that augments an independent clause with additional information, but which cannot stand alone as a sentence. Dependent clauses either modify the independent clause of a sentence or serve as a component of it.

This is quite clear — the dependent clause has some relation to the independent clause of the sentence. The role of independent clause in our case is taken by "doesn't mean B", but it lacks something. I quote Wikipedia:

An independent clause (or main clause) is a clause that can stand by itself, also known as a simple sentence. An independent clause contains a subject and a predicate; it makes sense by itself.

Clearly, the purportedly independent clause is not independent, because it does not have a subject and doesn't make sense by itself. We have a dependent clause, but no independent clause, and that's not grammatical English.

"Just because... doesn't mean" constructions are surely only colloquial (and not very elegant) ways of saying something like "From the fact that X is the case it does not follow/should not be inferred that Y is the case".